1. Field of the Invention
The invention relates to apparatus, illustratively a tandem telephone switch, for providing telephonic mass announcement service and to methods for use therein in providing passive and/or interactive announcements as well as interactive mass announcement based customized call routing services.
2. Description of the Prior Art
For a number of years, many local telephone companies ("telcos") have provided their callers with various dial-up mass announcement services. Through these services, a caller dials a given telephone number and then, after a telephone connection is established, receives a particular recorded voice (audio) message associated with that number. The correct time and forecasted weather were the first announcements that were provided by most local telcos. Owing to the ease with which a caller could obtain timely information, these announcement services, though passive in nature (i.e. permitting no caller interaction other than dialing into an announcement number), became very popular with callers.
Currently, an increasingly wide array of mass announcement services, both passive (non-interactive) and interactive, the latter requiring a caller to dial a number to select an entry from a pre-defined menu(s) of available choices provided by the announcement in order to obtain a selected service, are being offered to telephone callers by private information providers (IPs) over telephone network connections provided by the local telcos. These providers prepare each announcement itself, receive telephone calls for these announcements over the network from requesting telephone callers and, for passive announcements, play announcements back to these callers through the network while, for interactive announcements, solicit information from each of these callers during the announcement to subsequently provide a desired service thereto. For reasons that will shortly become clear, IPs have generally limited their use of interactive announcements to non-call routing applications. Nevertheless, over the past five years, IPs have been offering an increasingly broad and diverse spectrum of audio services accessible through dial-up passive mass announcement offerings that goes well beyond mere time and weather information to encompass for example stock quotations, sports scores, ticket availability for various special events and other services based upon rendering specific timely information and through dial-up interactive announcements that encompasses for example merchandise ordering services and the like. Because these offerings satisfied wide and heretofore unfilled needs of callers for a broad range of inexpensive easily accessible timely information and/or for telephonic ordering services, these offerings produced a substantial increase in the demand for and usage of mass announcement services. As such, mass announcement services now generate a significant source of revenue for both IPs and the local telephone companies. Unfortunately, the number of subscriber numbers which has been allocated by the telcos to carry mass announcements has not kept up with the increasing demand for announcement services. Accordingly, the availability of new mass announcement services has been severely limited in many telephone service areas and, in conjunction with capacity limitations as discussed below and inherent in the manner through which announcement services are currently being provided by available mass announcement equipment, this frequently causes callers to experience some degree of aggravation and/or frustration in receiving mass announcements.
In particular, mass announcement services are provided through announcement equipment located at each IP. To provide a simple non-interactive voice announcement, an IP would merely use an analog voice storage device for announcement storage and playback along with an appropriate network interface that connects and interfaces this storage device to a dedicated telephone line. This device, in its simplest form, could be an analog tape recorder that plays a continuous loop of tape. Voice announcements, whether passive or even interactive, are generally provided on a non-barge-in first-come first-serve basis to successive telephone callers. Accordingly, with such a voice storage device, any new caller would need to wait until an announcement then being played to a prior caller once again reached its starting point before the new caller would be able to hear it. Since announcements are frequently a minute or more in duration, the delay ("latency") experienced by a caller in waiting for an announcement to repeat before he or she is able to hear it could maximally amount to slightly less than the length of the entire announcement and hence be quite annoying. In an effort to reduce the delay, phased announcements are widely used today. Here, three separate identical recordings of the same announcement are continually played on three separate corresponding dedicated telephone lines. Playback is configured such that an equal delay interval, which amounts to twenty seconds for a one minute announcement, occurs between the start of any two of these recordings. An incoming caller is connected to that recording which is the next to start. Through phased announcements, the maximum latency can be reduced to slightly less than one third of the total announcement time but this is still sufficiently long to aggravate many callers.
Moreover, call volume frequently exceeds the number of line terminations that is available on the announcement equipment. Consequently, individual callers are often placed in a first-in first-out queue and remain there until corresponding terminations subsequently become available. If the queue is long, then the length of time that a caller remains in the queue, i.e. the "holding" (queuing) delay, can become significant. In fact, certain announcements can generate such a heavy call volume that the queue rapidly fills before only a few callers receive the announcement. To cope with this situation, a central office that serves an IP may either throttle the call volume to an announcement number down to match the rate at which the queue is emptying or just block all subsequent calls to this number, by providing a busy signal to all subsequent callers, until the incoming call volume thereto subsides to a sufficiently low level. In either case, a large number of calls to this announcement will likely be blocked and result in lost revenue to this IP and to the telco that carries the call traffic.
At first blush, one might think that the incidence of blocked calls along with latency and holding delays can all be reduced by using additional groups of three dedicated lines and accompanying duplicated announcement equipment to handle incoming calls. This approach is quite problematic. First, announcement call traffic often exhibits very sharp peaks at irregular intervals and is substantially reduced at all other times. Using sufficient numbers of separate dedicated lines and duplicated phased announcement equipment to satisfactorily accommodate all incoming calls that would occur during any such peak would be extremely expensive for an IP and result in significant inefficiencies. As such, IPs attempt to design their announcement systems to handle a certain expected average call volume for a given announcement and consequently force callers, during periods of heavy call traffic, to tolerate a certain amount of latency and holding delay and a certain level of call blockage. Unfortunately, the average call volume for any announcement is often extremely difficult to estimate with any acceptable degree of accuracy thereby complicating the design and particularly the sizing of an announcement system. Second, apart from difficulties associated with designing the announcement system itself, a shortage of available announcement numbers currently exists in many sections of the country. In particular, as the popularity of announcement services, both passive and interactive, has substantially increased over the past few years, many telcos either are exhausting or have already exhausted the subscriber numbers that have been allocated to carry announcement services. As a result, new announcement services can not be offered in many sections of the country and many existing IPs face difficulty in obtaining new numbers to handle, even apart from traffic peaks, increases in expected average call volume for announcements already in service.
Thus, the limitations of traditional announcement equipment and capacity limitations experienced by the telcos in providing additional network connections, i.e. announcement numbers, have disadvantageously slowed the growth of new announcement services and the growth in revenues attainable thereby to both IPs and the telcos themselves.
While various attempts have been made in the art to overcome certain drawbacks associated with the manner in which announcement services are currently being provided, none of these attempts has proven to be completely satisfactory. One such attempt described in U.S. Pat. Nos. 4,357,493 (issued to T. W. Anderson et al on Nov. 2, 1982) and 4,446,336 (issued to L. D. Bethel et al on May 1, 1984) utilizes a mass announcement system that is connected to a toll switching system. This announcement system stores separate passive announcements in digitized pulse code modulated (PCM) form on a disk unit. Whenever an announcement is activated for service, that announcement is then transferred from the disk to a number of playback buffers for transmittal to subsequent callers. The same passive announcement is stored within each of these buffers but with an identical phase delay, typically 30 seconds, between any two successive playback buffers. The output of each playback buffer in the mass announcement circuit is continuously applied through a time slot interchange (TSI) circuit that feeds a time multiplex switching matrix (TSM) within the toll switching system. A "nailed-up" connection within the TSM itself connects one TSI circuit to another TSI circuit, the latter having a looped back connection. By virtue of these connections, the passive announcement residing in any one playback buffer can be continuously "fanned out" through these and other TSI circuits and the TSM to multiple available time slots and therethrough, in turn, to multiple callers. The time slots for each playback buffer are assigned to incoming calls that arrive closest to the relative starting time of the announcement residing in that buffer. While this mass announcement system accommodates an increased number of callers without using additional announcement numbers, callers are still grouped to hear the same passive announcement residing in each playback buffer. As such, each caller, depending upon the time at which his or her call arrived at the switching system relative to the time at which the start of the announcement will be read from the assigned playback buffer, will likely experience some latency up to a maximum of 30 seconds prior to hearing the announcement. This latency may frustrate and/or aggravate that caller.
Another attempt at providing passive announcements is described in U.S. Pat. No. 4,817,086 (issued to K. J. Oye on Mar. 28, 1989). Here, an announcement circuit, connected to a communication system through time division multiplexed (TDM) and packet busses, locally stores a passive announcement in compressed digitized PCM form. For playback, the system instructs the announcement circuit as to which time slot to use and which passive announcement to play thereon. Unfortunately, the announcement circuit can only play 16 different announcements at any one time, thereby severely limiting the number of different passive announcements that can be simultaneously accessed therethrough. As such, this announcement circuit is not readily amenable to simultaneously handling a large number of different passive announcements.
As noted above, interactive announcements are now seeing increasing use in a wide range of applications. However, very few of these applications involve call routing. One such call routing application involves embedding an interactive announcement within a local private branch exchange (PBX) for use in automatically routing an incoming call to a particular extension based upon a caller's dialed response to information requested therefrom by the announcement. Here, a caller is greeted by a voice announcement providing welcoming information followed by a subsequent request to the caller to enter a specific digit(s) from a verbal menu of choices in order to obtain a desired service or department. Once the digit(s) is entered, the PBX appropriately routes the call to its proper recipient. Through use of these announcements, a local PBX can automatically route a large number of incoming calls to appropriate extensions using a relatively small number of human operators.
Although IPs perceive a significant demand for offering customized call routing services using interactive announcements, it is currently uneconomic, in most instances, for them to provide these services. Specifically, an IP is connected to the telephone network at an end of a voice path established by a telco and routed thereby between a caller and that provider. Accordingly, if that IP were to re-route incoming calls on a customized basis, such as through use of an interactive announcement, that provider would essentially need to replicate a certain portion of the switching functions provided by the telco. This, in turn, would necessitate that the IP obtain a large number of dedicated lines and/or trunks from the telco for use in appropriately re-routing incoming calls and also use relatively complex switching equipment to re-route these calls over these lines and/or trunks accordingly. Even if the IP could obtain a necessary number of lines and/or trunks from the telco, the combined expense of the switching equipment, the dedicated lines and/or trunks needed to support this announcement, switch programming and other start-up costs would be quite significant and likely cause the price of the interactive announcement based custom call routing service to exceed the amount which most of its potential callers would be willing to pay therefor. Hence, although a significant demand for these customized call routing services exists, these services are now rarely offered, if at all, by IPs.
Thus, a need exists in the art for a mass announcement system that can provide announcements with reduced latency and holding delays. Such an announcement system should also have the capability to advantageously handle a relatively large number of different announcements as well as handle peak call volumes on a substantially non-blocking basis. The system should advantageously accommodate both non-interactive and interactive announcements without requiring a large number of announcement numbers provided by a telco and also provide interactive announcement based custom call routing services at a relatively low cost to an IP, specifically without the need to employ expensive switching equipment at the IP or a large number of dedicated lines and/or trunks terminating thereat.